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Abundances from disentangled component spectra: the eclipsing binary V578 Mon
Chemical abundances of the early-B type components of the binary V578Mon are derived from disentangled component spectra. This is a pilotstudy showing that, even with moderately high line-broadening, metalabundances can be derived from disentangled spectra with a precision of0.1 dex, differential to sharp-lined single stars of the same spectraltype. This binary is well-suited to such an assessment because of itsyouth as a member of the Rosette Nebula cluster NGC 2244, strengtheningthe expectation of an unevolved ZAMS chemical composition. The method isuseful for studying rotationally driven mixing in main-sequence stars,since fundamental stellar parameters are known with higher accuracy in(eclipsing) binaries. This paper also evaluates of the bias that mightbe present in disentangled spectra.
| On the highly reddened members in six young galactic star clusters - a multiwavelength study
The spectral and reddening properties of 211 highly reddenedproper-motion members with V < 15 mag in six young galactic starclusters are investigated using low-resolution spectroscopic, broad-bandUBVRIJHK and mid-infrared (IR) data. We report emission features in CaIIHK and HI lines for a sample of 29 stars including 11 stars reported forthe first time and also provide either a new or more reliable spectralclass for a sample of 24 stars. CaII triplet width measurements are usedto indicate the presence of an accretion disc for a dozen stars and toindicate luminosity for a couple of stars. On the basis of spectralfeatures, near-IR excesses, dereddened colour-colour diagrams and mid-IRspectral indices we identify a group of 28 pre-main-sequence clustermembers including five highly probable Herbig Ae/Be and six classical TTauri stars. A total of 25 non-emission main-sequence (MS) stars,amounting to ~10 per cent early-type MS members, appears to showVega-like characteristics or are precursors to such a phenomenon. Thevarious membership indicators suggest that ~16 per cent of theproper-motion members are non-members. A significant fraction (>70per cent) of programme stars in NGC 1976, NGC 2244, NGC 6530 and NGC6611 show anomalous reddening with RV= 4.78 +/- 0.10, 3.54+/- 0.04, 3.87 +/- 0.05 and 3.56 +/- 0.02, respectively, indicating thepresence of grain size dust larger than that typical of the diffusemedium. A small number of stars in NGC 1976, NGC 2244 and NGC 6611 alsoshow normal behaviour while the cluster NGC 6823 appears to have normalreddening. Three highly luminous late-type giants, one in NGC 2244 andtwo in NGC 6530, appear to be members and are inpost-hydrogen-core-burning stages, suggesting a prolonged duration (~25Myr) of star formation.
| 10 MK Gas in M17 and the Rosette Nebula: X-Ray Flows in Galactic H II Regions
We present the first high spatial resolution X-ray images of twohigh-mass star forming regions, the Omega Nebula (M17) and the RosetteNebula (NGC 2237-2246), obtained with the Chandra X-Ray ObservatoryAdvanced CCD Imaging Spectrometer instrument. The massive clusterspowering these H II regions are resolved at the arcsecond level intomore than 900 (M17) and 300 (Rosette) stellar sources similar to thoseseen in closer young stellar clusters. However, we also detect softdiffuse X-ray emission on parsec scales that is spatially and spectrallydistinct from the point-source population. The diffuse emission hasluminosity LX~=3.4×1033 ergs s-1in M17 with plasma energy components at kT~=0.13 and ~=0.6 keV (1.5 and7 MK), while in Rosette it has LX~=6×1032ergs s-1 with plasma energy components at kT~=0.06 and ~=0.8keV (0.7 and 9 MK). This extended emission most likely arises from thefast O star winds thermalized either by wind-wind collisions or by atermination shock against the surrounding media. We establish that onlya small portion of the wind energy and mass appears in the observeddiffuse X-ray plasma; in these blister H II regions, we suspect thatmost of it flows without cooling into the low-density interstellarmedium. These data provide compelling observational evidence that strongwind shocks are present in H II regions.
| A Method for Simultaneous Determination of AV and R and Applications
A method for the simultaneous determination of the interstellarextinction (AV) and of the ratio of total to selectiveextinction (R), derived from the 1989 Cardelli, Clayton, & Mathisfitting of the interstellar extinction law, is presented and applied toa set of 1900 color excesses derived from observations of stars inUBVRIJHKL. The method is used to study the stability of AVand R within selected regions in Perseus, Scorpius, Monoceros, Orion,Sagittarius, Ophiuchus, Carina, and Serpens. Analysis shows that R isapproximately constant and peculiar to each sector, with mean valuesthat vary from 3.2 in Perseus to 5.6 in Ophiuchus. These results aresimilar to published values by Aiello et al., He et al., Vrba &Rydgren, O'Donnell, and Cardelli, Clayton, & Mathis.
| Observations of Star-Forming Regions with the Midcourse Space Experiment
We have imaged seven nearby star-forming regions, the Rosette Nebula,the Orion Nebula, W3, the Pleiades, G300.2-16.8, S263, and G159.6-18.5,with the Spatial Infrared Imaging Telescope on the Midcourse SpaceExperiment (MSX) satellite at 18" resolution at 8.3, 12.1, 14.7, and21.3 μm. The large angular scale of the regions imaged (~7.2-50deg2) makes these data unique in terms of the combination ofsize and resolution. In addition to the star-forming regions, twocirrus-free fields (MSXBG 160 and MSXBG 161) and a field near the southGalactic pole (MSXBG 239) were also imaged. Point sources have beenextracted from each region, resulting in the identification over 500 newsources (i.e., no identified counterparts at other wavelengths), as wellas over 1300 with prior identifications. The extended emission from thestar-forming regions is described, and prominent structures areidentified, particularly in W3 and Orion. The Rosette Nebula isdiscussed in detail. The bulk of the mid-infrared emission is consistentwith that of photon-dominated regions, including the elephant trunkcomplex. The central clump, however, and a line of site toward thenorthern edge of the cavity show significantly redder colors than therest of the Rosette complex.
| Strong Emission-Line Stars Identified toward the Rosette Nebula
Several strong emission-line stars were found in the opticalidentification of the ROSAT PSPC sources in the Rosette Nebula. Thesepossible X-ray emitters were classified from the low-resolution spectraobtained as Herbig Ae/Be type stars or probable weak-line T Tauri stars.A classical Be star was also identified around one of the X-ray sourcesstudied. Our study supports the conjecture that ROSAT X-ray observationscould trace low- and intermediate-mass star formation to a distance of~1.5 kpc.
| UBVI and Hα Photometry of the Young Open Cluster NGC 2244
New UBVI and Hα photometry has been performed for the young opencluster NGC 2244. We classified 30 OB stars as being members of thecluster using proper-motion data and spectral types from previousinvestigators, along with photometric diagrams obtained in this study.We measured Hα emission strength of the stars by Hαphotometry and set up a selection criterion to select pre-main-sequence(PMS) stars with Hα emission. Fourteen PMS stars and seven PMScandidates were found using the criterion. In addition, six stars foundnear the positions of ROSAT HRI X-ray sources were assumed to be PMSstars and the optical counterparts of these X-ray sources. We determineda reddening of =0.47+/-0.04 for the cluster and atotal-to-selective extinction ratio of RV=3.1+/-0.2. Thedistance modulus derived was V0-MV=11.1. Bycomparing our photometric results with theoretical evolution models, wederived a main-sequence turnoff age of 1.9 Myr and a PMS age spread ofabout 6 Myr. The slope of the initial mass function, Γ, calculatedin the mass range 0.5<=logm<=2.0 could be flat(Γ=-0.7+/-0.1).
| Spectral classification of O-M stars on the basis of UBV photometry
A new technique allowing the Q-method to be used surely for both thespectral classification of young O-A0 stars and older spectralsubclasses A1-M5 is described. Characteristics of interstellar lightabsorption dependence on distance in the given direction of the sky isused as a main criterion for excluding possible multiplicity of starspectral estimates at some constant values of QUBV.Information on open cluster membership probabilities is also useful asadditional criterion of the spectral classification. The method wastested on stars up to V=14 mag in directions of young open clusters NGC2244 and NGC 2264. The spectral study based on UBV photometry wasextended to faint stars of NGC 2264 in the V magnitude range 17-22 mag.
| UBV beta Database for Case-Hamburg Northern and Southern Luminous Stars
A database of photoelectric UBV beta photometry for stars listed in theCase-Hamburg northern and southern Milky Way luminous stars surveys hasbeen compiled from the original research literature. Consisting of over16,000 observations of some 7300 stars from over 500 sources, thisdatabase constitutes the most complete compilation of such photometryavailable for intrinsically luminous stars around the Galactic plane.Over 5000 stars listed in the Case-Hamburg surveys still lackfundamental photometric data.
| Spectroscopic analysis of early-type stars in young stellar groups. I. Differential analysis of the B1V stars in NGC 2244.
We explore the potential of analysing fast rotating early-type starsdifferentially with respect to templates derived from a slowly rotatingstar of the same spectral type. The analysis is successfully applied tothe normal B1V stars in NGC 2244, which have projected rotationalvelocities ranging from 22 to 260km/s. A classical non-LTE analysis ofthe slow rotator #201 results in chemical abundances similar to those ofearly B-type stars in the field and in Orion. We argue that adifferential analysis of the fast rotators relative to a broadenedtemplate derived from #201 can still reveal abundance differences of>0.2dex, but no evidence was found for differences in metalcomposition at this level. A differential analysis of H and He lineprofiles reveals the need to further explore rotation models. Neitherthe classical approach to stellar rotation, nor the published modelsthat include the influence of rotation on the star's atmosphere canbring the profiles of the slow rotator into complete agreement withthose of the fast rotators. An attempt to extend the analysis to a Bestar failed. The Be spectrum is described qualitatively and quantitativemeasurements are made for the emission in the core of the Balmer lines.
| The Initial Mass Function and Massive Star Evolution in the OB Associations of the Northern Milky Way
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995ApJ...454..151M&db_key=AST
| Vitesses radiales. Catalogue WEB: Wilson Evans Batten. Subtittle: Radial velocities: The Wilson-Evans-Batten catalogue.
We give a common version of the two catalogues of Mean Radial Velocitiesby Wilson (1963) and Evans (1978) to which we have added the catalogueof spectroscopic binary systems (Batten et al. 1989). For each star,when possible, we give: 1) an acronym to enter SIMBAD (Set ofIdentifications Measurements and Bibliography for Astronomical Data) ofthe CDS (Centre de Donnees Astronomiques de Strasbourg). 2) the numberHIC of the HIPPARCOS catalogue (Turon 1992). 3) the CCDM number(Catalogue des Composantes des etoiles Doubles et Multiples) byDommanget & Nys (1994). For the cluster stars, a precise study hasbeen done, on the identificator numbers. Numerous remarks point out theproblems we have had to deal with.
| An Einstein Observatory SAO-based catalog of B-type stars
About 4000 X-ray images obtained with the Einstein Observatory are usedto measure the 0.16-4.0 keV emission from 1545 B-type SAO stars fallingin the about 10 percent of the sky surveyed with the IPC. Seventy-fourdetected X-ray sources with B-type stars are identified, and it isestimated that no more than 15 can be misidentified. Upper limits to theX-ray emission of the remaining stars are presented. In addition tosummarizing the X-ray measurements and giving other relevant opticaldata, the present extensive catalog discusses the reduction process andanalyzes selection effects associated with both SAO catalog completenessand IPC target selection procedures. It is concluded that X-rayemission, at the level of Lx not less than 10 exp 30 ergs/s, is quitecommon in B stars of early spectral types (B0-B3), regardless ofluminosity class, but that emission, at the same level, becomes lesscommon, or nonexistent, in later B-type stars.
| Uvby-beta observations of 528 type B stars with V between the 8th and 9th magnitude
The paper presents uvby-beta measurements of 528 type B stars selectedfrom the SAO Catalog on the basis of two criteria: the spectral types inthe range B3-B5 and mV between the 8th and the 9th magnitude. Reddeningindependent (c1) values are estimated from the spectral classificationand compared to the observed values. No systematic trend with observed(b-y), H-beta, or spectral type appears to be present, but the range of(c1) residuals is surprisingly large. A rather large part of the starshas small beta values, smaller than for the BIa supergiants. Only twoare classified as O stars and most of them have the suffix e, ne, ornne. Most beta values for the O type stars are slightly above the upperlimit of 2.585 m.
| IRAS observations of the Rosette nebula complex
A detailed study of the infrared radiation associated with the Rosettenebula complex has been conducted using the IRAS data. The results ofthe study suggest that most of the infrared sources detected by IRASwhich are embedded in the Rosette molecular cloud are associated withdense molecular clumps. The luminosities of these sources cover therange 100-12,000 solar luminosities, corresponding to B1-B4 stellartypes.
| UVBY beta photometry of stars in the field of NGC 2244 and NGC 2264
Results are presented from uvby beta photometric observations of 34stars in the fields of NGC 2244 and NGC 2264. Photometric andastrometric indicators suggest that about a third of the sample arenonmembers of the clusters. Cluster color excesses are determined forthe two clusters. For the stars examined, log g and effectivetemperature are estimated. Also, stellar radii, masses, and positions inthe H-R diagram are calculated. The cluster ages and the main-sequencelifetime for massive stars show that star formation in the region hasnot been restricted to a single epoch.
| Trapezium-type wide systems
On the basis of the Smithsonian Observatory Catalogues 15 Trapezium-typesystems are found. Photometric distances are determined for theTrapezium components. A conclusion is drawn on physical relations of thecomponents in the systems. The fact of existence of Trapezium-type largestellar systems confirms the existence of Trapezia with positive totalenergy.
| On the distances to the young open clusters NGC 2244 and NGC 2264
A new determination of the distances of the young open clusters NGC 2244and NGC 2264 is presented. It is based on distance moduli for individualOB-type stars in which the influence of the anomalous ratio of total toselective extinction, if any, is taken into account. A discussion isincluded, first, of the accuracy of the color-difference method comparedto that of other current methods for determining R and, second, of theerrors in the determination of the distances for clusters embedded innonuniform H II regions. New photoelectric measurements (UBVRI andJHKLM), and new spectrophotometric data (IDS spectra) are presented forOB-type stars in these clusters as well as summaries of publishedphotometric data. The locations in the H-R diagram of the program starsseem to suggest that these massive stars are on the main sequence,supporting the idea of continuous star formation.
| Catalog of BV magnitudes and spectral classes of 6000 stars
The present catalog, compiled at the Abastumani Observatory, contains BVmagnitudes and spectral classes of about 6000 stars up to V(lim) = 13.0min five circular areas of 18 sq deg located near the salactic-equatorplane. The catalog is intended for star-statistics studies ofstar-formation regions.
| Additional Variable Stars in the Northern Luminous Stars Catalogues
Not Available
| UBV Photometry of NGC2244
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1981PASJ...33..149O&db_key=AST
| The influence of interstellar absorption on measured strengths of the Balmer discontinuity
The definition of the Balmer-discontinuity strength from observationalspectrophotometric data is discussed in relation to detailed results onthe wavenumber dependence of the interstellar absorption. The break inthe interstellar absorption curve at a wavenumber of about 2.33permicrons is found to introduce systematic errors in many currentlydefined strengths of the Balmer discontinuity. The errors should beproportional to the amount of the color excess caused by interstellarabsorption. Using the interstellar absorption curves established byDivan (1954) and by Nandy (1964) theoretical relations are derivedbetween the amount of interstellar absorption and the correspondinginfluence on the Balmer-discontinuity strength. These linear relationsare confirmed through tests on larger sets of observational data. At thesame time the derived relations are useful as correction formulas.
| UVBY beta photometry of NGC 2244.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1977AJ.....82..973H&db_key=AST
| Observations of interstellar reddening V,
Not Available
| Polarization in NGC2244
Not Available
| Study on Galactic Rotation Based on Radial Velocities, of OB Stars and O-Associations
Not Available
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Observation and Astrometry data
| Constellation: | Monoceros |
| Right ascension: | 06h31m33.47s |
| Declination: | +04°50'39.7" |
| Apparent magnitude: | 9.274 |
| Proper motion RA: | -1.9 |
| Proper motion Dec: | -0.3 |
| B-T magnitude: | 9.437 |
| V-T magnitude: | 9.288 |
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